Electrocoagulation products such as the electrocautery knife and, more recently, the argon beam coagulator are ubiquitous; both employ thermal techniques for cauterizing small, severed blood vessels, as well as gross damage to the capillary bed. However, these devices are largely ineffective for attaining hemostasis in highly vascularized tissues such as the liver and spleen, and they have a very limited depth of penetration - typically less than a millimeter. It has been demonstrated in a variety of animal experiments that high-intensity focused ultrasound (HIFU) can be employed to rapidly induce hemostasis in severed, hemorrhaging blood vessels up to several millimeters in diameter. Moreover, upon exposure to sufficient levels of focused ultrasound, arterial and venous blood flow can be greatly reduced in vessels located deep within highly perfused viscera such as the liver and spleen. The goal of our proposed research is to develop a new class of cauterization devices, based upon the use of HIFU, which will have broad applications in surgery and in emergency medicine. We call these devices intra-operative acoustic hemostasis devices and their use "acoustocauter?." We believe that acoustocautely devices can become standard equipment in operating rooms and emergency departments as commercial systems become available. PROPOSED COMMERCIAL APPLICATIONS: Cauterization devices are used in nearly every surgical procedure, with electrocautery the most dominant technology. Acoustocautery is a novel and innovative new technique that has several advantages over electrocautery and represents a potentially strong competitor to all forms of cautery. We propose to construct a variety of acustocautery devices that would have broad applications in clinical medicine.